Among the innovations originated by the government--which were none the less innovations, that almost uniformly they changed not the letter, but merely the practice of the existing constitution--the most prominent were the measures by which the filling up of officers' posts as well as of civil magistracies was made to depend not, as the letter of the constitution allowed and its spirit required, simply on merit and ability, but more and more on birth and seniority. As regards the nomination of staff-officers this was done not in form, but all the more in substance. It had already, in the course of the previous period, been in great part transferred from the general to the burgesses;(13) in this period came the further step, that the whole staff-officers of the regular yearly levy--the twenty-four military tribunes of the four ordinary legions--were nominated in the -comitia tributa-. Thus a line of demarcation more and more insurmountable was drawn between the subalterns, who gained their promotion from the general by punctual and brave service, and the staff, which obtained its privileged position by canvassing the burgesses.(14) With a view to check simply the worst abuses in this respect and to prevent young men quite untried from holding these important posts, it became necessary to require, as a preliminary to the bestowal of staff appointments, evidence of a certain number of years of service. Nevertheless, when once the military tribunate, the true pillar of the Roman military system, was laid down as the first stepping-stone in the political career of the young aristocrats, the obligation of service inevitably came to be frequently eluded, and the election of officers became liable to all the evils of democratic canvassing and of aristocratic exclusiveness. It was a cutting commentary on the new institution, that in serious wars (as in 583) it was found necessary to suspend this democratic mode of electing officers, and to leave once more to the general the nomination of his staff. Restrictions on the Election of Consuls and Censors